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X-Nuclei MRI and Energy Metabolism
Published in Guillaume Madelin, X-Nuclei Magnetic Resonance Imaging, 2022
The creatine kinase (CK) is an enzyme that catalyzes the reversible conversion reaction between creatine (Cr) and ATP, and phospho-creatine (PCr) and ADP:ADP+PCr⇌ATP+Cr. This enzyme can be present in different cells in the body, but mostly in tissues with high rates of energy transfer or rapid fluctuations in energy requirement, such as muscles, brain, photoreceptor cells, or spermatozoa. In such cells, PCr serves as a reservoir for rapid buffering and regeneration of ATP through CK reaction when ATP produced by glycolysis and cellular respiration is in short supply for cell function [28].
Clinical Applications of Immunoassays
Published in Richard O’Kennedy, Caroline Murphy, Immunoassays, 2017
Cardiac troponin serum levels (TnT and TnI) are the most sensitive and specific markers of myocardial damage as they are found in higher abundance in heart muscle than other cardiac enzymes and, therefore, have a higher detectable concentration in serum following cardiac injury [16]. Serum levels rise within 3–12 hours from the onset of chest pain and peak at 24 hours before normalising by days 3–10. Peak values correlate with the extent of cardiac injury. It is important to note that a rise and/or fall in the troponin level over a fixed period of time is one of the criteria for the diagnosis of an acute myocardial infarction. A level greater than the 99th percentile value for the immunoassay is regarded as a positive result [17]. Although the troponins are specific for cardiac damage, there are variations in the sensitivity and specificity of the immunoassay used in the detection of troponin levels, and therefore local guidelines should be consulted prior to interpretation [18, 19]. The main reasons for this variation are a lack of standardisation, differences in antibody cross-reactivity to skeletal muscle and degradation products of TnI, and the presence of modified TnI and TnT which interferes with true assay values [20, 21]. Creatine kinase comprises three isoenzymes: CK-MM (found mainly in skeletal muscle), CK-BB (found mainly in brain) and CK-MB (found mainly in the heart). Most assays measure CK-MB mass, as it avoids the detection of macrokinases (CK linked to IgG and dimers of mitochondrial CK), which can interfere with enzyme activity assays [22]. A rise in CK-MB is relatively specific for cardiac muscle injury; however, because CK-MB can be released from skeletal muscle, it can lead to falsely elevated levels in chronic skeletal muscle diseases such as that seen in dermatomyositis and polymyositis, and therefore troponins are the preferred cardiac biomarker in acute coronary syndrome [23, 24].
Dose-response and temporal ergogenic effects of ginseng supplementation in athletes and active participants: A systematic review and meta-analysis
Published in Journal of Sports Sciences, 2022
Nasreen Khan, Saurabh Sharma, Indu Dahiya, Junaid Khan, Shalini Sharma, Raj Kumar Sharma
CK is the enzyme responsible for catalysing the conversion of creatine and adenosine triphosphate (ATP) to phosphocreatine and adenosine diphosphate (ADP; Brancaccio et al., 2007; Sayers & Clarkson, 2003). The presence of CK in the blood is thought to be an indirect indication of muscle injury (Baird et al., 2012; Totsuka et al., 2002). Serum CK levels in the general population range from 20 to 200 IU/L and may rise following eccentric activity due to skeletal muscle damage (Armstrong et al., 1983; Moghadam-Kia et al., 2016). The CK activity levels in the included studies were assessed using four different approaches. First, blood was collected before and after the uphill treadmill exercise test (H. L. Jung et al., 2011). Second, blood was collected before and after the downhill treadmill exercise test (Pumpa et al., 2013). Third, blood samples were obtained after the participants completed four dynamic sets of half-squats with eccentric action at 70% of 1-RM until concentric failure (Cristina-Souza et al., 2022). Fourth, the participants completed an exhausting pedalling test in which the speed and power of the bike were simultaneously increased every 1 minute until volitional tiredness, followed by blood CK level measurements (Chen et al., 2021).
Glyphosate-based herbicide impairs energy metabolism and increases autophagy in C6 astroglioma cell line
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Katriane Neto da Silva, Laura Garbin Cappellaro, Caroline Naomi Ueda, Luana Rodrigues, Aline Pertile Remor, Roberta de Paula Martins, Alexandra Latini, Viviane Glaser
Another enzyme related to energy metabolism, CK, was also inhibited by glyphosate-based herbicide in C6 cells exposed for 24 h. CK catalyzes the reversible transfer of a phosphoryl groups between ATP and creatine and plays a key role in energy metabolism of tissues that display high and fluctuating energy requirements, such as nervous tissue (Wallimann and Hemmer 1994). Our results demonstrated that CK is more sensitive to pesticide exposure than other enzymes related to energetic metabolism, since a concentration of 80 μM inhibited enzymatic activity. It is noteworthy that alterations in CK activity were noted in CNS diseases associated with changes in energy metabolism and may represent an important step in a neurodegenerative pathway that leads to neuronal loss in CNS (Hemmer et al. 1994; Tomimoto et al. 1993). CK is susceptible to damage initiated by ROS due to a critical cysteinyl residue at its active site; consequently, this enzyme is susceptible to inactivation by oxidative reactions (Aksenov et al. 2000; Kenyon 1996; Konorev, Hogg, and Kalyanaraman 1998; Wang et al. 2001).
Effect of rest period configurations on systemic inflammatory response in resistance-trained women
Published in Journal of Sports Sciences, 2021
Hui-Ying Luk, Margaret T. Jones, Jakob L. Vingren
Serum creatine kinase concentrations were determined by a colorimetric method (C7522150, Pointe Scientific, Canton, MI) using an automated chemistry analyser (Chemwell, Awareness Technologies, Palm City, FL). The detection limit for this assay is 1500 U∙L−1 and it demonstrates linearity from 25– 1500 U∙L−1.